Setting the 'replication_factor' property is only valid for SimpleStrategy. For NetworkTopologyStrategy you need to specify the name of a datacenter and the replication factor for that data center. So your command:

stategy_options:replication_factor=2

is actually saying put 2 copies of the data in the datacenter named 'replication_factor'. What you really want is something along the lines of:

stategy_options:DC1=2 and strategy_options:DC2=2

Part of the documentation here is wrong and I will make sure to get it fixed: